The invention relates generally to multiple friction plate clutches for motor vehicles and more specifically to clutches for motor vehicle drive line components having an internal reaction force circuit.
Vehicle drive line and control systems having both electric and hydraulic modulating clutches have found broad application in adaptive vehicle drive systems. Such systems generally monitor the speeds of the front and rear drive shaft or compute such speeds by taking averages of individual readings of the two front and two rear wheels and, upon determining a speed difference between the drive shaft speeds or average speeds of the wheels, energize the modulating clutch according to a predetermined program to drive the speed difference and thus wheel slip toward zero. Such systems may also monitor and adjust modulating clutch activity in response to throttle position, steering angle and other variables.
Typically, such modulating clutches are physically disposed in a transfer case, adjacent and driven by the output of the vehicle transmission, and operably disposed between the primary and secondary drive lines. Such systems are disposed in co-owned U.S. Pat. No. 5,407,024 granted Apr. 18, 1995 and 5,485,894 granted Jan. 23, 1996.
An alternate approach to vehicle skid control comprehends association of an individually operable clutch with each axle of a secondary, that is, part-time drive line. Selective, modulating activation of one or both of the clutches directs drive torque to one or both secondary drive wheels to adjust or correct vehicle yaw. An early system utilizing hydraulic clutches is disclosed in U.S. Pat. No. 4,681,180. Here, a control unit having steering angle, vehicle speed and engine torque inputs and adjust torque distribution between only the two rear wheels.
U.S. Pat. No. 5,195,901 and 5,119,900 both teach a vehicle having two independently operable rear axle clutches in a drive line which provides primary drive torque to the front wheels and selectively to the rear wheels.
In U.S. Pat. No. 5,353,889 a rear axle includes a pair of hydraulically operated independent clutches controlled by a associated hydraulic pressure clutches and pumps.
In U.S. Pat. No. 5,383,378, a twin clutch axle disposed at the front of a vehicle provide drive torque to the front (secondary) drive wheel in response to steering angle. U.S. Pat. No. 5,540,119 teaches a differential drive assembly for transferring rotational power without the use of conventional differential gearing. The device utilizes pairs of clutches and cam mechanisms which actuate said clutches in response a predetermined relative rotation.
While many problems have been addressed and new operational schemes achieved by the devices found in the prior art, it is apparent that certain problems have not been addressed. For example, it should be appreciated that, according to Newton's third law of motion, the direct or action force generated by a clutch operator to compress an adjacent clutch pack creates an equal and opposite reaction force which is transmitted through whatever structural components of the clutch assembly constitute the reaction force path or circuit.
Typically, such reaction force path will be through or contained in an outer housing in devices where the clutch pack is disposed adjacent the clutch operator and both are contained within the housing. Such a configuration can apply significant reaction force, not only to the housing, but also to whatever fasteners are utilized to secure the housing components together. Such a configuration can be disadvantageous, causing either fastener or housing failure or necessitate heavy and therefore costly housing and fastener configurations. Accurately controlled modulation of the clutches may also be compromised due to flexure or distortion of the housing or other components in the reaction force path. Accordingly, the operation of devices containing such clutches may be compromised. The present invention addresses such matters.